Photostable UV-screening compositions comprising dibenzoylmethane/diarylbutadiene compounds

ABSTRACT

Topically applicable, photostable cosmetic/dermatological UV-screening compositions comprise (a) at least one photolabile UV-screening dibenzoylmethane compound and (b) a dibenzoylmethane photostabilizing amount of at least one 4,4-diarylbutadiene compound, formulated into a topically applicable, cosmetically/dermatologically acceptable support therefor; the weight ratio of the 4,4-diarylbutadiene compound(s) to the diarylbutadiene compound(s) is characteristically greater than 2.5 and the subject compositions are advantageously devoid of any cinnamate sunscreen.

CROSS-REFERENCE TO PRIORITY/PCT APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119 ofFR-00/16518, filed Dec. 18, 2000, and is a continuation ofPCT/FR01/03635, filed Nov. 20, 2001 and designating the United States(published in the French language on Jun. 27, 2002 as WO 02/49595 A2;the title and abstract were also published in English), both herebyexpressly incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field of the Invention

[0003] The present invention relates to cosmetic or dermatologicalcompositions for topical application, more particularly in a regime orregimen for photoprotecting the skin and the hair, comprising, inadmixture, a UV-screening agent of the dibenzoylmethane derivative typeand a 4,4-diarylbutadiene compound.

[0004] The present invention also relates to a process for improving thestability towards UV radiation of at least one dibenzoylmethanederivative, which entails combining with said dibenzoylmethanederivative, an effective amount of at least one 4,4-diarylbutadienecompound.

[0005] 2. Description of Background/Related/Prior Art

[0006] It is known that light radiation with wavelengths of between 280nm and 400 nm permit tanning of the human epidermis and that light rayswith wavelengths more particularly between 280 and 320 nm, known as UV-Brays, cause skin burns and erythema which can harm the development of anatural tan. For these reasons, as well as for aesthetic reasons, thereis a constant demand for means of controlling this natural tanning inorder thus to control the color of the skin; this UV-B radiation shouldthus be screened out.

[0007] It is also known that UV-A rays, with wavelengths between 320 and400 nm, which cause browning of the skin, are liable to induce adversechanges therein, in particular in the case of sensitive skin or skinwhich is continually exposed to solar radiation. UV-A rays cause inparticular a loss of elasticity of the skin and the appearance ofwrinkles leading to premature aging of the skin. They promote triggeringof the erythemal reaction or amplify this reaction in certainindividuals and may even be the cause of phototoxic or photoallergicreactions. Thus, for aesthetic and cosmetic reasons such as theconservation of the skin's natural elasticity, for example, anincreasingly large number of individuals wish to control the effect ofUV-A rays on their skin. It is thus desirable also to screen out UV-Aradiation.

[0008] In this respect, one particularly advantageous family of UV-Ascreening agents currently consists of dibenzoylmethane derivatives, andin particular 4-tert-butyl-4′-methoxydibenzoylmethane, which have highintrinsic absorbing power. These dibenzoylmethane derivatives, which areproducts which are now well known per se as screening agents that areactive in the UV-A range, are described in particular in FR-A-2-326,405and FR-A-2-440,933, as well as in EP-A-0-114,607;4-tert-butyl-4′-methoxydibenzoylmethane is moreover currently sold underthe trademark “Parsol 1789” by Hoffmann LaRoche.

[0009] Unfortunately, it is found that dibenzoylmethane derivatives areproducts that are relatively sensitive to ultraviolet radiation(especially UV-A), i.e., more specifically, they have an annoyingtendency to degrade more or less quickly under the action of thisradiation. Thus, this substantial lack of photochemical stability ofdibenzoylmethane derivatives towards ultraviolet radiation, to whichthey are by nature intended to be subjected, does not make it possibleto ensure constant protection during prolonged exposure to sunlight, andas a result repeated applications at regular and close intervals must bemade by the user in order to obtain effective protection for the skinagainst UV rays.

[0010] EP-0-967,200, DE-197,46,654, DE-197,55,649, EP-1-008,586,DE-100,07,017, EP-1-133,980 and EP-1-133,981 disclose antisuncompositions based on 4,4-diarylbutadienes, which may contain otheradditional screening agents, such as dibenzoylmethane derivatives.

SUMMARY OF THE INVENTION

[0011] It has now unexpectedly and surprisingly been determined thatimprovedly photostable cosmetic or dermatological compositions fortopical application are provided, formulated into a cosmeticallyacceptable support, which comprise:

[0012] (a) at least one UV-screening agent of the dibenzoylmethanederivative type, and

[0013] (b) at least one 4,4-diarylbutadiene compound; the weight ratioof the 4,4-diarylbutadiene compound to the dibenzoylmethane derivativebeing greater than 2.5 and said composition advantageously containing nocinnamate sunscreen.

[0014] The present invention also features a process for improving thestability towards UV radiation of at least one dibenzoylmethanederivative, which entails combining with said dibenzoylmethanederivative an effective amount of at least one 4,4-diarylbutadienecompound.

DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OFTHE INVENTION

[0015] More particularly, in accordance with the present invention, theexpression “effective amount of 4,4-diarylbutadiene” means an amountthat is sufficient to obtain an appreciable and significant improvementin the photostability of the dibenzoylmethane derivative or derivativesin the photoprotective cosmetic composition. This minimum amount ofphotostabilizing agent to be used, which may vary depending on thenature of the cosmetically acceptable support selected for thecomposition, may be determined without difficulty by means of a standardtest for measuring photostability.

[0016] Also in accordance with the invention, the term“4,4-diarylbutadiene compound” means any molecule comprising at leastone 4,4-diarylbutadiene chromophoric group. This molecule may be in theform of a simple compound, an oligomer or a polymer having, on thechain, grafts comprising the chromophoric group.

[0017] Lastly, the present invention also features the use of a4,4-diarylbutadiene compound for the preparation of a cosmetic ordermatological composition comprising at least one dibenzoylmethanederivative, in order to improve the stability towards UV rays of thesaid dibenzoylmethane derivative therein.

[0018] Other characteristics, aspects, embodiments and advantages of thepresent invention will become apparent from the detailed descriptionthat follows.

[0019] Among the preferred 4,4-diarylbutadiene compounds in accordancewith the invention that may be selected are the compounds correspondingto formula (I) below:

[0020] in which the diene system is of Z,Z; Z,E; E,Z or E,Econfiguration or mixtures of the said configurations, and in which:

[0021] R¹ and R², which may be identical or different, denote hydrogen,a linear or branched C₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; aC₁-C₁₂ alkoxy radical; a C₃-C₁₀ cycloalkyl radical; a C₃-C₁₀cycloalkenyl radical; a linear or branched C₁-C₂₀ alkoxycarbonylradical; a linear or branched C₁-C₁₂ monoalkylamino radical; a linear orbranched C₁-C₁₂ dialkylamino radical; an aryl radical; a heteroarylradical or a hydro-solubilizing substituent which comprises acarboxylate group, a sulfonate group or an ammonium residue;

[0022] R³ denotes a group COOR⁵; COR⁵; CONR⁵R⁶; CN; a linear or branchedC₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; a C₃-C₁₀ cycloalkylradical; a C₇-C₁₀ bicycloalkyl radical; a C₃-C₁₀ cycloalkenyl radical; aC₇-C₁₀ bicycloalkenyl radical; a C₆-C₁₈ aryl radical; a C₃-C₇ heteroarylradical;

[0023] R⁴ denotes a group COOR⁶; COR⁶; CONR⁵R⁶; CN; a linear or branchedC₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; a C₃-C₁₀ cycloalkylradical; a C₇-C₁₀ bicycloalkyl radical; a C₃-C₁₀ cycloalkenyl radical; aC₇-C₁₀ bicycloalkenyl radical; an aryl radical; a heteroaryl radical;

[0024] R⁵ and R⁶, which may be identical or different, denote hydrogen;[X]_(p)-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-PO₃Y;C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; a linear or branched C₁-C₂₀ alkyl radical; aC₂-C₁₀ alkenyl radical; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀bicycloalkyl radical; a C₃-C₁₀ bicycloalkenyl radical; a C₇-C₁₀cycloalkenyl radical; an aryl radical; a heteroaryl radical;

[0025] X denotes a group —CH₂—CH₂-Z-, —CH₂CH₂CH₂Z-, —CH(CH₃)—CH₂-Z-,—CH₂—CH₂—CH₂—CH₂-Z- or —CH₂—CH(CH₂CH₃)-Z-;

[0026] A denotes Cl, Br, I or SO₄R⁹;

[0027] Y denotes hydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺

[0028] Z denotes O or NH;

[0029] R⁷ and R⁸, which may be identical or different, denote hydrogen,a linear or branched C₁-C₆ alkyl radical; a linear or branched C₂-C₆alkenyl radical; a linear or branched C₁-C₆ acyl radical;

[0030] R⁹ denotes hydrogen, a linear or branched C₁-C₆ alkyl radical; aC₂-C₆ alkenyl radical;

[0031] n ranges from 1 to 3;

[0032] p ranges from 0 to 150.

[0033] Examples of C₁-C₂₀ alkyl radicals that may be mentioned are:methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl,2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl,2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl,n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl,2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl,1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl,2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl,1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl,n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl,n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl,n-nonadecyl or n-eicosyl.

[0034] Examples of C₂-C₁₀ alkenyl groups that may be mentioned are:ethenyl, n-propenyl, 1-methylethenyl, n-butenyl, 1-methylpropenyl,2-methylpropenyl, 1,1-dimethylethenyl, n-pentenyl, 1-methylbutenyl,2-methylbutenyl, 3-methylbutenyl, 2,2-dimethylpropenyl, 1-ethylpropenyl,n-hexenyl, 1,1-dimethylpropenyl, 1,2-dimethylpropenyl, 1-methylpentenyl,2-methylpentenyl, 3-methylpentenyl, 4-methylpentenyl,1,1-dimethylbutenyl, 1,2-dimethylbutenyl, 1,3-dimethylbutenyl,2,2-dimethylbutenyl, 2,3-dimethylbutenyl, 3,3-dimethylbutenyl,1-ethylbutenyl, 2-ethylbutenyl, 1,1,2-trimethyl-propenyl,1,2,2-trimethylpropenyl, 1-ethyl-1-methyl-propenyl,1-ethyl-2-methylpropenyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl.

[0035] As C₁-C₁₂ alkoxy radicals, mention may be made of: methoxy,n-propoxy, 1-methylpropoxy, 1-methylethoxy, n-pentoxy, 3-methylbutoxy,2,2-dimethylpropoxy, 1-methyl-1-ethylpropoxy, octoxy, ethoxy, n-propoxy,n-butoxy, 2-methylpropoxy, 1,1-dimethylpropoxy, hexoxy, heptoxy,2-ethylhexoxy.

[0036] Examples of C₃-C₁₀ cycloalkyl radicals which may be mentionedare: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,1-methylcyclopropyl, 1-ethylcyclopropyl, 1-propylcyclopropyl,1-butylcyclopropyl, 1-pentylcyclopropyl, 1-methyl-1-butylcyclopropyl,1,2-dimethylcyclopropyl, 1-methyl-2-ethylcyclopropyl, cyclooctyl,cyclononyl or cyclodecyl.

[0037] As C₃-C₁₀ cycloalkenyl radicals containing one or more doublebonds, mention may be made of: cyclobutenyl, cyclopentenyl,cyclopentadienyl, cyclohexenyl, 1,3-cyclohexadienyl,1,4-cyclohexadienyl, cycloheptenyl, cycloheptatrienyl, cyclooctenyl,1,5-cyclooctadienyl, cyclooctatetraenyl, cyclononenyl or cyclodecenyl.

[0038] The cycloalkyl or cycloalkenyl radicals may comprise one or more(preferably from 1 to 3) substituents chosen, for example, from halogen,for instance chlorine, fluorine or bromine; cyano; nitro; amino; C₁-C₄alkylamino; C₁-C₄ dialkylamino; C₁-C₄ alkyl; C₁-C₄ alkoxy; hydroxyl;they may also comprise from 1 to 3 hetero atoms, for instance sulfur,oxygen or nitrogen, the free valencies of which may be satisfied with ahydrogen or a C₁-C₄ alkyl radical.

[0039] Examples of acyl radicals that may be mentioned include formyl,acetyl, propionyl and n-butyryl.

[0040] The bicycloalkyl or bicycloalkenyl groups are chosen, forexample, from bicyclic terpenes, for instance pinane, bornane, pinene,camphor or adamantane derivatives.

[0041] The aryl groups are preferably chosen from phenyl and naphthylrings, which may contain one or more (preferably from 1 to 3)substituents chosen, for example, from halogen, for instance chlorine,fluorine or bromine; cyano; nitro; amino; C₁-C₄ alkylamino; C,-C₄dialkylamino; C₁-C₄ alkyl; C₁-C₄ alkoxy; hydroxyl. Phenyl, methoxyphenyl and naphthyl are more particularly preferred.

[0042] The heteroaryl groups generally comprise one or more hetero atomschosen from sulfur, oxygen and nitrogen.

[0043] The hydro-solubilizing groups are, for example, carboxylate orsulfonate groups and more particularly salts thereof withphysiologically acceptable cations, for instance the alkali metal saltsor trialkylammonium salts such as the tris(hydroxy alkyl)ammonium or2-methyl-1-propanol-2-ammonium salts. Mention may also be made ofammonium groups, for instance alkylammoniums and forms thereof salifiedwith physiologically acceptable anions.

[0044] The preferred compounds of formula (I) are chosen from those offormula (Ia) below:

[0045] in which the diene system is of Z,Z; Z,E; E,Z or E,Econfiguration or mixtures of the said configurations, and in which:

[0046] R¹ and R², which may be identical or different, denote hydrogen,a C₁-C₈ alkyl radical; a C₁-C₈ alkoxy radical; a hydro-solubilizingsubstituent chosen from a carboxylate group, a sulfonate group and anammonium residue;

[0047] R³ denotes a group COOR⁵; CONR⁵R⁶; CN;

[0048] R⁴ denotes a group COOR⁶; CONR⁵R⁶;

[0049] R⁵ denotes hydrogen; [X]_(p)R⁷; C₁-C₆ alkylene-SO₃Y; C₁-C₆alkylene-N(R⁸)₃ ⁺A⁻;

[0050] R⁶ denotes [X]_(p)-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆ alkylene-N(R⁸)₃^(+A) ⁻;

[0051] X denotes a —CH₂—CH₂—O—, —CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O— group;

[0052] A denotes Cl, Br, I or SO₄R⁹;

[0053] Y denotes hydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺

[0054] R⁷, R⁸ and R⁹, which may be identical or different, denotehydrogen or a linear or branched C₁-C₃ alkyl radical;

[0055] n ranges from 1 to 3;

[0056] p ranges from 0 to 50.

[0057] The compounds of formula (I) that are even more preferred arechosen from those corresponding to formula (Ib) below:

[0058] in which the diene system is of Z,Z; Z,E; E,Z or E,Econfiguration or mixtures of the said configurations, and in which:

[0059] R¹ and R², which may be identical or different, denote hydrogen,a C₁-C₈ alkyl radical; a C₁-C₈ alkoxy radical;

[0060] R³ denotes a group COOR⁵; CONR⁵R⁶; CN;

[0061] R⁴ denotes a group COOR⁶; CONR⁵R⁶;

[0062] R⁵ denotes hydrogen; [X]_(p)-R⁷; C₁-C₆-alkylene-SO₃Y;C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻;

[0063] R⁶ denotes [X]P-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃⁺A⁻;

[0064] X denotes a —CH₂—CH₂—O—, —CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O—group;

[0065] A denotes Cl, Br, I or SO₄R⁹;

[0066] Y denotes hydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li^(+, Al) ³⁺ or —N(R⁸)₄⁺

[0067] R⁷, R⁸ and R⁹, which may be identical or different, denotehydrogen or a linear or branched C₁-C₃ alkyl radical;

[0068] p ranges from 0 to 50.

[0069] The compounds of formula (I) that are even more preferred arechosen from those corresponding to formula (Ic) below:

[0070] in which the diene system is of Z,Z; Z,E; E,Z or E,Econfiguration or mixtures of the said configurations, and in which:

[0071] R¹ and R², which may be identical or different, denote hydrogen,a C₁-C₈ alkyl radical; a C₁-C₈ alkoxy radical;

[0072] R³ denotes a group COOR⁵; CONR⁵R⁶; CN;

[0073] R⁴ denotes a group COOR⁶; CONR⁵R⁶;

[0074] R⁵ denotes hydrogen; [X]_(p)-R⁷; C₁-C₆-alkylene-SO₃y;C₁-C₆-alkylene-N(R⁸)₃ ^(+A) ⁻;

[0075] R⁶ denotes [X]_(p)-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃⁺A⁻;

[0076] X denotes a —CH₂—CH₂—O—, —CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O—group;

[0077] A denotes Cl, Br, I or SO₄R⁹;

[0078] Y denotes hydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺

[0079] R⁷, R⁸ and R⁹, which may be identical or different, denotehydrogen or a linear or branched C₁-C₃ alkyl radical;

[0080] p ranges from 0 to 50.

[0081] The compounds of formula (I) that are even more particularlypreferred are chosen from the following compounds:

[0082] The compounds of formula (I) as defined above are known per seand their structures and syntheses are described in EP-0-967,200,DE-197,46,654 and DE-197,55,649 (which form an integral part of thecontent of the description).

[0083] Among the preferred 4,4-diarylbutadiene compounds in accordancewith the invention that may also be mentioned are the oligomerscorresponding to formula (II) below:

[0084] in which the diene system is of Z,Z; Z,E; E,Z or E,Econfiguration or mixtures of the said configurations, and in which:

[0085] R¹, R², R³ and n have the same definitions as in formula (I)above;

[0086] Y′ denotes a group —O— or —NR¹⁰—;

[0087] R¹⁰ denotes hydrogen; a linear or branched C₁-C₂₀ alkyl radical;a C₂-C₁₀ alkenyl radical; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀bicycloalkyl radical; a C₃-C₁₀ cycloalkenyl radical; a C₇-C₁₀bicycloalkenyl radical; an aryl radical; a heteroaryl radical;

[0088] X′ denotes an aliphatic or cycloaliphatic linear or branchedpolyol residue comprising from 2 to 10 hydroxyl groups and of valency q;the carbon-based chain of the said residue optionally being interruptedwith one or more sulfur or oxygen atoms; one or more imine groups; oneor more C₁-C₄ alkylimino groups;

[0089] q ranges from 2 to 10.

[0090] X′ is a polyol residue containing from 2 to 10 hydroxyl groupsand especially:

[0091] The compounds of formula (II) that are more preferred are thosefor which:

[0092] R¹ and R², which may be identical or different, denote hydrogen,a C₁-C₁₂ alkyl radical; a C₁-C₈ alkoxy radical; a hydro-solubilizingsubstituent chosen from a carboxylate group, a sulfonate group and anammonium residue;

[0093] R³ denotes a group COOR⁵; CONR⁵R⁶; CN; a C₃-C₁₀ cycloalkylradical; a C₇-C₁₀ bicycloalkyl radical;

[0094] R⁵ and R⁶, which may be identical or different, denote a linearor branched C₁-C₂₀ alkyl radical; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀bicycloalkyl radical; optionally substituted naphthyl or phenyl;

[0095] X′ denotes a polyol residue comprising from 2 to 6 and moreparticularly from 2 to 4 hydroxyl groups.

[0096] The compounds of formula (II) that are even more preferred arethose for which:

[0097] x′ denotes an ethanol or pentaerythrol residue.

[0098] The compounds of formula (II) that are even more particularlypreferred are chosen from the following compounds:

[0099] The compounds of formula (II) as defined above are known per seand their structures and syntheses are described in EP-A-1,008,586(which forms an integral part of the content of the description).

[0100] The 4,4-diarylbutadiene compounds in accordance with theinvention are preferably present in the composition of the invention inproportions ranging from 0.5% to 15% by weight and more preferably from1% to 10% by weight, relative to the total weight of the composition.

[0101] As mentioned above, the dibenzoylmethane derivativesphotostabilized within the scope of the present invention are productsthat are already well known per se and described in particular inFR-2-326,405, FR-2-440,933 and EP-0-114,607, the teachings of whichdocuments are, as regards the actual definition of these products,entirely included as references in the present description.

[0102] According to the present invention, one or more dibenzoylmethanederivatives can of course be used.

[0103] Among the dibenzoylmethane derivatives which fall particularlywell within the scope of the present invention, mention may be made inparticular, in a non-limiting manner, of:

[0104] 2-methyldibenzoylmethane

[0105] 4-methyldibenzoylmethane

[0106] 4-isopropyldibenzoylmethane

[0107] 4-tert-butyldibenzoylmethane

[0108] 2,4-dimethyldibenzoylmethane

[0109] 2,5-dimethyldibenzoylmethane

[0110] 4,4′-diisopropyldibenzoylmethane

[0111] 4,4′-dimethoxydibenzoylmethane

[0112] 4-tert-butyl-4′-methoxydibenzoylmethane

[0113] 2-methyl-5-isopropyl-4′-methoxydibenzoylmethane

[0114] 2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane

[0115] 2,4-dimethyl-4′-methoxydibenzoylmethane

[0116] 2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane.

[0117] Among the dibenzoylmethane derivatives mentioned above, it ismost particularly preferred to use, according to the present invention,4-(tert-butyl)-4′-methoxydibenzoylmethane, in particular the productsold under the trademark “Parsol 1789” by Hoffmann LaRoche, thisscreening agent corresponding to the structural formula below:

[0118] Another dibenzoylmethane derivative which is preferred accordingto the present invention is 4-isopropyldibenzoylmethane, this screeningagent being sold under the name “Eusolex 8020” by Merck andcorresponding to the structural formula below:

[0119] The dibenzoylmethane derivative(s) may be present in thecompositions in accordance with the invention in contents ranging from0.5% to 15% by weight and more particularly from 1% to 10% by weight,relative to the total weight of the composition.

[0120] The compositions in accordance with the invention may alsocomprise other additional organic UV-screening agents that are active inthe UVA and/or UVB range (absorbers), which are water-soluble orliposoluble or even insoluble in the cosmetic solvents commonly used.

[0121] The additional organic UV-screening agents are especially chosenfrom anthranilates; salicylic derivatives; camphor derivatives; triazinederivatives such as those described in U.S. Pat. No. 4,367,390,EP-863,145, EP-517,104, EP-570,838, EP-796,851, EP-775,698, EP-878,469and EP-933,376; benzophenone derivatives; β,β-diphenylacrylatederivatives; benzotriazole derivatives, benzimidazole derivatives;imidazolines; p-aminobenzoic acid (PABA) derivatives;methylenebis(hydroxyphenyl)benzotriazole derivatives as described inU.S. Pat. Nos. 5,237,071, 5,166,355, GB-2-303,549, DE-197-26,184 andEP-893,119; screening polymers and screening silicones such as thosedescribed especially in WO 93/04665; dimers derived from α-alkylstyrene,such as those described in DE-198,55,649.

[0122] As examples of organic screening agents, mention may be made ofthe following, denoted herein below under their INCI name:

[0123] Para-Aminobenzoic Acid Derivatives:

[0124] PABA,

[0125] Ethyl PABA,

[0126] Ethyl dihydroxypropyl PABA,

[0127] Ethylhexyl dimethyl PABA sold in particular under the name“Escalol 507” by ISP,

[0128] Glyceryl PABA,

[0129] PEG-25 PABA sold under the name “Uvinul P25” by BASF.

[0130] Salicylic Derivatives:

[0131] Homosalate sold under the name “Eusolex HMS” by Rona/EMIndustries,

[0132] Ethylhexyl salicylate sold under the name “Neo Heliopan OS” byHaarmann and Reimer,

[0133] Dipropylene glycol salicylate sold under the name “Dipsal” byScher,

[0134] TEA salicylate sold under the name “Neo Heliopan TS” by Haarmannand Reimer.

[0135] Dibenzoylmethane Derivatives

[0136] Butyl methoxydibenzoylmethane sold in particular under thetrademark “Parsol 1789” by Hoffmann LaRoche,

[0137] Isopropyl dibenzoylmethane.

[0138] β,β′-Diphenyl Acrylate Derivatives:

[0139] Octocrylene sold in particular under the trademark “Uvinul N539”by BASF,

[0140] Etocrylene sold in particular under the trademark “Uvinal N35” byBASF.

[0141] Benzophenone Derivatives:

[0142] Benzophenone-1 sold under the trademark “Uvinul 400” by BASF,

[0143] Benzophenone-2 sold under the trademark “Uvinul D50” by BASF,

[0144] Benzophenone-3 or Oxybenzone sold under the trademark “UvinulM40” by BASF,

[0145] Benzophenone-4 sold under the trademark “Uvinul MS40” by BASF,

[0146] Benzophenone-5,

[0147] Benzophenone-6 sold under the trademark “Helisorb 11” by Norquay,

[0148] Benzophenone-8 sold under the trademark “Spectra-Sorb UV-24” byAmerican Cyanamid,

[0149] Benzophenone-9 sold under the trademark “Uvinul DS-49” by BASF,

[0150] Benzophenone-12.

[0151] Benzylidenecamphor Derivatives:

[0152] 3-Benzylidenecamphor manufactured under the name “Mexoryl SD” byChimex,

[0153] 4-Methyl benzylidenecamphor sold under the name “Eusolex 6300” byMerck,

[0154] Benzylidenecamphor sulfonic acid manufactured under the name“Mexoryl SL” by Chimex,

[0155] Camphor benzalkonium methosulfate manufactured under the name“Mexoryl SO” by Chimex,

[0156] Terephthalylidenedicamphorsulfonic acid manufactured under thename “Mexoryl SX” by Chimex,

[0157] Polyacrylamidomethylbenzylidenecamphor manufactured under thename “Mexoryl SW” by Chimex.

[0158] Phenyl Benzimidazole Derivatives:

[0159] Phenylbenzimidazolesulfonic acid sold in particular under thetrademark “Eusolex 232” by Merck,

[0160] Benzimidazilate sold under the trademark “Neo Heliopan AP” byHaarmann and Reimer.

[0161] Triazine Derivatives:

[0162] Anisotriazine sold under the trademark “Tinosorb S” by CibaSpecialty Chemicals

[0163] Ethylhexyl triazone sold in particular under the trademark“Univul T150” by BASF,

[0164] Diethylhexyl butamido triazone sold under the trademark “UvasorbHeb” by Sigma 3V,

[0165] 2,4,6-tris(Diisobutyl 4′-aminobenzalmalonate)s-triazine.

[0166] Phenyl Benzotriazole Derivatives:

[0167] Drometrizole trisiloxane sold under the name “Silatrizole” byRhodia Chimie,

[0168] Methylenebis(benzotriazolyl)tetramethylbutylphenol sold in solidform under the trademark “MIXXIM BB/100” by Fairmount Chemical, or inmicronized form as an aqueous dispersion under the trademark “TinosorbM” by Ciba Specialty Chemicals.

[0169] Anthranilic Derivatives:

[0170] Menthyl anthranilate sold under the trademark “Neo Heliopan MA”by Haarmann and Reimer.

[0171] Imidazoline Derivatives:

[0172] Ethylhexyldimethoxybenzylidenedioxoimidazoline propionate.

[0173] Benzalmalonate Derivatives:

[0174] Polyorganosiloxane containing benzalmalonate functions, soldunder the trademark “Parsol SLX” by Hoffmann LaRoche and mixturesthereof.

[0175] The organic UV-screening agents that are more particularlypreferred are chosen from the following compounds:

[0176] Ethylhexyl salicylate,

[0177] Octocrylene,

[0178] Phenylbenzimidazolesulfonic acid,

[0179] Terephthalylidenedicamphorsulfonic acid,

[0180] Benzophenone-3,

[0181] Benzophenone-4,

[0182] Benzophenone-5,

[0183] 4-Methylbenzylidenecamphor,

[0184] Disodium phenyl dibenzimidazole tetrasulfonate,

[0185] Anisotriazine,

[0186] Ethylhexyl triazone,

[0187] Diethylhexyl butamido triazone,

[0188] 2,4,6-tris(Diisobutyl 4′-aminobenzalmalonate)-s-triazine,

[0189] Methylenebis(benzotriazolyl)tetramethylbutylphenol,

[0190] Drometrizole trisiloxane, and mixtures thereof.

[0191] The cosmetic compositions according to the invention may alsocomprise pigments or nanopigments (average size of the primaryparticles: generally between 5 nm and 100 nm and preferably between 10nm and 50 nm) of coated or uncoated metal oxides, such as, for example,nanopigments of titanium oxide (amorphous or crystallized in rutileand/or anatase form), of iron oxide, of zinc oxide, of zirconium oxideor of cerium oxide, which are all UV photoprotective agents that arewell known per se. Standard coating agents are, moreover, alumina and/oraluminum stearate. Such coated or uncoated metal oxide nanopigments aredescribed in particular in EP-A-0-518,772 and EP-A-0-518,773.

[0192] The compositions according to the invention may also containagents for artificially tanning and/or browning the skin (self-tanningagents) such as, for example, dihydroxyacetone (DHA).

[0193] The compositions of the invention may also comprise standardcosmetic adjuvants and additives chosen especially from fattysubstances, organic solvents, ionic or nonionic thickeners, softeners,antioxidants, free-radical scavengers, opacifiers, stabilizers,emollients, silicones, α-hydroxy acids, antifoams, moisturizers,vitamins, insect repellants, fragrances, preserving agents, surfactants,anti-inflammatories, substance P antagonists, fillers, polymers,propellants, acidifying or basifying agents, colorants or any otheringredient usually used in cosmetics, in particular for the manufactureof antisun compositions in the form of emulsions.

[0194] The fatty substances may consist of an oil or a wax or mixturesthereof. The term “oil” means a compound that is liquid at roomtemperature. The term “wax” means a compound that is solid orsubstantially solid at room temperature, and whose melting point isgenerally above 35° C. They also comprise linear or cyclic fatty acids,fatty alcohols and fatty acid esters such as benzoic acid, trimelliticacid and hydroxybenzoic acid derivatives.

[0195] Oils that may be mentioned include mineral oils (paraffin); plantoils (sweet almond oil, macadamia oil, blackcurrant pip oil or jojobaoil); synthetic oils, for instance perhydrosqualene, fatty alcohols,fatty acids or fatty esters (for instance the C₁₂-C₁₅ alkyl benzoatessold under the trademark “Finsolv TN” by Finetex, octyl palmitate,isopropyl lanolate, triglycerides including capric/caprylic acidtriglycerides), oxyethylenated or oxypropylenated fatty esters andethers; silicone oils (cyclomethicone, and polydimethylsiloxanes orPDMS) or fluoro oils, and polyalkylenes.

[0196] Waxy compounds that may be mentioned include paraffin, carnaubawax, beeswax and hydrogenated castor oil.

[0197] Among the organic solvents that may be mentioned are loweralcohols and polyols.

[0198] Nonetheless, a person skilled in the art will take care to selectthis or these optional additional compound(s) and/or the amounts thereofsuch that the advantageous properties, in particular the photostability,intrinsically associated with the compositions in accordance with theinvention are not, or are not substantially, adversely affected by theenvisaged addition(s).

[0199] The compositions of the invention may be prepared according totechniques that are well known to those skilled in the art, inparticular those intended for preparing emulsions of oil-in-water orwater-in-oil type.

[0200] These compositions may be in particular in the form of a simpleemulsion or a complex emulsion (O/W, W/O, O/W/O or W/O/W), such as acream, a milk, a gel or a cream-gel; a powder or a solid tube, and mayoptionally be packaged as an aerosol and may be in the form of a mousseor spray.

[0201] When it is an emulsion, the aqueous phase of this emulsion maycomprise a nonionic vesicular dispersion prepared according to knownprocesses (Bangham, Standish and Watkins, J. Mol. Biol. 13, 238 (1965),FR-2-315,991 and FR-2-416,008).

[0202] The cosmetic composition of the invention may be topicallyapplied as a composition for protecting the human epidermis or the hairagainst ultraviolet rays, as an antisun composition or as a makeupproduct.

[0203] When the cosmetic composition according to the invention isadministered in a regime or regimen for protecting the human epidermisagainst UV rays, or as an antisun composition, it may be in the form ofa suspension or a dispersion in solvents or fatty substances, in theform of a nonionic vesicular dispersion or in the form of an emulsion,preferably of oil-in-water type, such as a milk or a cream, or in theform of an ointment, a gel, a cream-gel, a solid tube, a powder, astick, an aerosol mousse or a spray.

[0204] When the cosmetic composition according to the invention isemployed for protecting the hair against UV rays, it may be in the formof a shampoo, a lotion, a gel, an emulsion or a nonionic vesiculardispersion and may constitute, for example, a rinse-out composition, tobe applied before or after shampooing, before or after dyeing orbleaching, or before, during or after permanent-waving or straighteningthe hair, a styling or treating lotion or gel, a blow-drying orhairsetting lotion or gel, or a permanent-waving, straightening, dyeingor bleaching composition for the hair.

[0205] When the composition is used as a makeup product for theeyelashes, the eyebrows or the skin, such as an epidermal treatmentcream, a foundation, a tube of lipstick, an eyeshadow, a face powder,mascara or an eyeliner, it may be in solid or pasty, anhydrous oraqueous form, for instance oil-in-water or water-in-oil emulsions,nonionic vesicular dispersions or suspensions.

[0206] As a guide, for the antisun formulations in accordance with theinvention that contain a support of oil-in-water emulsion type, theaqueous phase (especially comprising the hydrophilic screening agents)generally represents from 50% to 95% by weight and preferably from 70%to 90% by weight, relative to the total weight of the formulation, theoily phase (especially comprising the lipophilic screening agents) from5% to 50% by weight and preferably from 10% to 30% by weight, relativeto the total weight of the formulation, and the (co)emulsifier(s) from0.5% to 20% by weight and preferably from 2% to 10% by weight, relativeto the total weight of the formulation.

[0207] As indicated above, the present invention features the use of acomposition as defined above for the manufacture of a cosmetic ordermatological composition suited for protecting the skin and/or thehair against ultraviolet radiation, in particular solar radiation.

[0208] The present invention also features a process for improving thestability of at least one dibenzoylmethane derivative towards UVradiation, which entails combining with said dibenzoylmethanederivative, an effective amount of at least one 4,4-diarylbutadiene asdefined above.

[0209] This invention also features the use of a UV-screening agent ofthe 4,4-diarylbutadiene type as defined above in the preparation of acosmetic or dermatological composition comprising at least oneUV-screening agent of the dibenzoylmethane derivative type, with theobjective of improving the stability of said dibenzoylmethane derivativetowards UV rays.

[0210] In order to further illustrate the present invention and theadvantages thereof, the following specific examples are given, it beingunderstood that same are intended only as illustrative and in nowiselimitative.

[0211] In said examples to follow, all parts and percentages are givenby weight, unless otherwise indicated.

[0212] The following Tables 1 and 2 report Examples 1 and 2, specificcompositions according to the invention. TABLE 1 COMPOSITION EXAMPLE 1Glyceryl mono/distearate/polyethylene  2 glycol stearate (100 EO)mixture (Arlacel 165 FL-ICI) Stearyl alcohol (Lanette 18-Henkel)  1Stearic acid from palm oil (Stearine  2.5 TP-Stearinic Dubois)Polydimethylsiloxane (Dow Corning  0.5 200 Fluid-Dow Corning) C12/C15alkyl benzoate (Witconol TN-  20 WITCO) Triethanolamine  0.5Butylmethoxydibenzoylmethane  2 (Parsol 1789-Hoffmann LaRoche) Compoundof formula (1)  8 Glycerol  4 Triethanolamine  0.3 Polyacrylic acid(Synthalen K-3V)  0.4 Preserving agents qs Demineralized water qs 100 g

[0213] TABLE 2 COMPOSITION EXAMPLE 2 Glycerylmono/distearate/polyethylene  2 glycol stearate (100 EO) mixture(Arlacel 165 FL-ICI) Stearyl alcohol (Lanette 18-Henkel)  1 Stearic acidfrom palm oil (Stearine  2.5 TP-Stearinerie Dubois) Polydimethylsiloxane(Dow Corning  0.5 200 Fluid-Dow Corning) C12/C15 alkyl benzoate(Witconol TN-  20 WITCO) Triethanolamine Butylmethoxydibenzylmethane  2(Parsol 1789-Hoffmann LaRoche) Compound of formula (6)  8 Glycerol  4Triethanolamine  0.3 Polyacrylic acid (Synthalen K-3V)  0.4 Preservingagents qs Demineralized water qs 100 g

[0214] Each patent, patent application and literature article/reportcited or indicated herein is hereby expressly incorporated by reference.

[0215] While the invention has been described in terms of variousspecific and preferred embodiments, the skilled artisan will appreciatethat various modifications, substitutions, omissions, and changes may bemade without departing from the spirit thereof. Accordingly, it isintended that the scope of the present invention be limited solely bythe scope of the following claims, including equivalents thereof.

What is claimed is:
 1. A topically applicable, photostablecosmetic/dermatological UV-screening composition, comprising: (a) atleast one UV-screening dibenzoylmethane compound and (b) adibenzoylmethane photostabilizing amount of at least one4,4-diarylbutadiene compound, formulated into a topically applicable,cosmetically/dermatologically acceptable support therefor.
 2. Thephotostable cosmetic/dermatological composition as defined by claim 1,the weight ratio of said at least one diarylbutadiene compound to saidat least one dibenzoylmethane compound being greater than 2.5 and saidcomposition being devoid of any cinnamate sunscreen.
 3. The photostablecosmetic/dermatological composition as defined by claim 1, said at leastone diarylbutadiene compound having the formula (I) below:

in which the diene system is of Z,Z; Z,E; E,Z or E,E configuration ormixtures of the said configurations, and in which the radicals R¹ andR², which may be identical or different, are each hydrogen, a linear orbranched C₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; a C₁-C₁₂ alkoxyradical; a C₃-C₁₀ cycloalkyl radical; a C₃-C₁₀ cycloalkenyl radical; alinear or branched C₁-C₂₀ alkoxycarbonyl radical; a linear or branchedC₁-C₁₂ monoalkylamino radical; a linear or branched C₁-C₁₂ dialkylaminoradical; an aryl radical; a heteroaryl radical or a hydro-solubilizingsubstituent which comprises a carboxylate group, a sulfonate group or anammonium residue; R³ is a group COOR⁵; COR⁵; CONR⁵R⁶; CN; a linear orbranched C₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; a C₃-C₁₀cycloalkyl radical; a C₇-C₁₀ bicycloalkyl radical; a C₃-C₁₀ cycloalkenylradical; a C₇-C₁₀ bicycloalkenyl radical; a C₆-C₁₈ aryl radical; a C₃-C₇heteroaryl radical; R⁴ is a group COOR⁶; COR⁶; CONR⁵R⁶; CN; a linear orbranched C₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenyl radical; a C₃-C₁₀cycloalkyl radical; a C₇-C₁₀ bicycloalkyl radical; a C₃-C₁₀ cycloalkenylradical; a C₇-C₁₀ cycloalkenyl radical; an aryl radical; a heteroarylradical; the radicals R⁵ and R⁶, which may be identical or different,are each hydrogen; [X]^(p)-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-PO₃Y;C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; a linear or branched C₁-C₂₀ alkyl radical; aC₂-C₁₀ alkenyl radical; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀bicycloalkyl radical; a C₃-C₁₀ cycloalkenyl radical; a C₇-C₁₀bicycloalkenyl radical; an aryl radical; a heteroaryl radical; X is agroup —CH₂—CH₂-Z-, —CH₂CH₂CH₂Z-, —CH(CH₃)—CH₂-Z-, —CH₂—CH₂—CH₂—CH₂-Z- or—CH₂—CH(CH₂CH₃)-Z-; A is Cl, Br, I or SO₄R⁹; Y is hydrogen, Na⁺, K⁺,Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺; Z is O or NH; the radicals R⁷ andR⁸, which may be identical or different, are each hydrogen, a linear orbranched C₁-C₆ alkyl radical; a linear or branched C₂-C₆ alkenylradical; a linear or branched C₁-C₆ acyl radical; R⁹ is hydrogen, alinear or branched C₁-C₆ alkyl radical; a C₂-C₆ alkenyl radical; nranges from 1 to 3; and p ranges from 0 to
 150. 4. The photostablecosmetic/dermatological composition as defined by claim 3, in which thecompound of formula (I) has the formula (Ia) below:

in which the diene system is of Z,Z; Z,E; E,Z or E,E configuration ormixtures of the said configurations, and in which the radicals R¹ andR², which may be identical or different, are each hydrogen, a C₁-C₈alkyl radical; a C₁-C₈ alkoxy radical; a hydro-solubilizing substituentwhich comprises a carboxylate group, a sulfonate group or an ammoniumresidue; R³ is a group COOR⁵; CONR⁵R⁶; CN; R⁴ is a group COOR⁶; CONR⁵R⁶;R⁵ is hydrogen; [X]_(p)-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃⁺A⁻; R⁶ is [X]P-R⁷; C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; X isa —CH₂—CH₂—O—, —CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O—group; A is Cl, Br, I orSO₄R⁹; Y is hydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺; theradicals R⁷, R⁸ and R⁹, which may be identical or different, are eachhydrogen or a linear or branched C₁-C₃ alkyl radical; n ranges from 1 to3; and p ranges from O to
 50. 5. The photostable cosmetic/dermatologicalcomposition as defined by claim 3, in which the compound of formula (I)has the formula (Ib) below:

in which the diene system is of Z,Z; Z,E; E,Z or E,E configuration ormixtures of the said configurations, and in which the radicals R¹ andR², which may be identical or different, are each hydrogen, a C₁-C₈alkyl radical; a C₁-C₈ alkoxy radical; R³ is a group COOR⁵; CONR⁵R⁶; CN;R⁴ is a group COOR⁶; CONR⁵R⁶; R⁵ is hydrogen; [X]P-R⁷;C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; R⁶ is [X]_(p)-R⁷;C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; X is a —CH₂—CH₂—O—,—CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O—group; A is Cl, Br, I or SO₄R⁹; Y ishydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺; the radicals R⁷,R⁸ and R⁹, which may be identical or different, are each hydrogen or alinear or branched C₁-C₃ alkyl radical; and p ranges from 0 to
 50. 6.The photostable cosmetic/dermatological composition as defined by claim3, in which the compound of formula (I) has the formula (Ic) below:

in which the diene system is of Z,Z; Z,E; E,Z or E,E configuration ormixtures of the said configurations, and in which the radicals R¹ andR², which may be identical or different, are each hydrogen, a C₁-C₈alkyl radical; a C₁-C₈ alkoxy radical; R³ is a group COOR⁵; CONR⁵R⁶; CN;R⁴ is a group COOR⁶; CONR⁵R⁶; R⁵ is hydrogen; [X]_(p)-R⁷;C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; R⁶ is [X]_(p)-R⁷;C₁-C₆-alkylene-SO₃Y; C₁-C₆-alkylene-N(R⁸)₃ ⁺A⁻; X is a —CH₂—CH₂—O—,—CH₂CH₂CH₂O—, —CH(CH₃)—CH₂—O—group; A is Cl, Br, I or SO₄R⁹; Y ishydrogen, Na⁺, K⁺, Mg²⁺, Ca²⁺, Li⁺, Al³⁺ or —N(R⁸)₄ ⁺; the radicals R⁷,R⁸ and R⁹, which may be identical or different, are each hydrogen or alinear or branched C₁-C₃ alkyl radical; and p ranges from 0 to
 50. 7.The photostable cosmetic/dermatological composition as defined by claim3, in which the compound of formula (I) is selected from among thefollowing compounds:


8. The photostable cosmetic/dermatological composition as defined byclaim 1, said at least one 4,4-diarylbutadiene compound comprising anoligomer having the formula (II) below:

in which the diene system is of Z,Z; Z,E; E,Z or E,E configuration ormixtures of the said configurations, and in which R¹, R², R³ and n havethe same definitions as in formula (I); Y′ is a group —O— or —NR¹⁰—; R¹⁰is hydrogen; a linear or branched C₁-C₂₀ alkyl radical; a C₂-C₁₀ alkenylradical; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀ bicycloalkyl radical; aC₃-C₁₀ cycloalkenyl radical; a C₇-C₁₀ bicycloalkenyl radical; an arylradical; a heteroaryl radical; X′ is an aliphatic or cycloaliphaticlinear or branched polyol residue comprising from 2 to 10 hydroxylgroups and of valency q; the carbon-based chain of said residueoptionally being interrupted with one or more sulfur or oxygen atoms;one or more imine groups or one or more C₁-C₄ alkylimino groups; and qranges from 2 to
 10. 9. The photostable cosmetic/dermatologicalcomposition as defined by claim 8, wherein the oligomer of formula (II),the radicals R¹ and R², which may be identical or different, are eachhydrogen, a C₁-C₁₂ alkyl radical; a C₁-C₈ alkoxy radical; ahydro-solubilizing substituent which comprises a carboxylate group, asulfonate group or an ammonium residue; R³ is a group COOR⁵; CONR⁵R⁶;CN; a C₃-C₁₀ cycloalkyl radical; a C₇-C₁₀ bicycloalkyl radical; theradials R⁵ and R⁶, which may be identical or different, are each alinear or branched C₁-C₂₀ alkyl radical; a C₃-C₁₀ cycloalkyl radical; aC₇-C₁₀ bicycloalkyl radical; or an optionally substituted naphthyl orphenyl; and X′ is a polyol residue comprising from 2 to 6 hydroxylgroups.
 10. The photostable cosmetic/dermatological composition asdefined by claim 9, wherein said compound of formula (II), X′ is anethanol or pentaerythrol residue.
 11. The photostablecosmetic/dermatological composition as defined by claim 8, said at leastone oligomer of formula (II) comprising at least one of:


12. The photostable cosmetic/dermatological composition as defined byclaim 1, said at least one dibenzoylmethane compound being selected fromthe group consisting of: 2-methyldibenzoylmethane,4-methyldibenzoylmethane, 4-isopropyldibenzoylmethane,4-tert-butyldibenzoylmethane, 2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane, 4,4′-diisopropyldibenzoylmethane,4,4′-dimethoxydibenzoylmethane, 4-tert-butyl-4′-methoxydibenzoylmethane,2-methyl-5-isopropyl-4′-methoxydibenzoylmethane,2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane,2,4-dimethyl-4′-methoxydibenzoylmethane,2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoyl-methane, and mixturesthereof.
 13. The photostable cosmetic/dermatological composition asdefined by claim 12, said at least one dibenzoylmethane compoundcomprising 4-(tert-butyl)-4-methoxydibenzoylmethane.
 14. The photostablecosmetic/dermatological composition as defined by claim 12, said atleast one dibenzoylmethane compound comprising4-isopropyldibenzoylmethane.
 15. The photostable cosmetic/dermatologicalcomposition as defined by claim 1, said at least one 4,4-diarylbutadienecompound comprising from 0.5% to 15% by weight thereof.
 16. Thephotostable cosmetic/dermatological composition as defined by claim 15,said at least one 4,4-diarylbutadiene compound comprising from 1% to 10%by weight thereof.
 17. The photostable cosmetic/dermatologicalcomposition as defined by claim 15, said at least one dibenzoylmethanecompound comprising from 0.5% to 15% by weight thereof.
 18. Thephotostable cosmetic/dermatological composition as defined by claim 16,said at least one dibenzoylmethane compound comprising from 1% to 10% byweight thereof.
 19. The photostable cosmetic/dermatological compositionas defined by claim 1, further comprising at least one other UV-A-activeand/or UV-B-active organic screening agent.
 20. The photostablecosmetic/dermatological composition as defined by claim 19, said atleast one other organic UV-screening agent being selected from the groupconsisting of anthranilates; salicylic derivatives; camphor derivatives;benzophenone derivatives; β,β′-diphenylacrylate derivatives;benzotriazole derivatives; benzalmalonate derivatives; benzimidazolederivatives; imidazolines; bis-benzazolyl derivatives; p-aminobenzoicacid (PABA) derivatives; methylenebis(hydroxyphenyl)benzotriazolederivatives; screening polymers and screening silicones; dimers derivedfrom α-alkylstyrene and mixtures thereof.
 21. The photostablecosmetic/dermatological composition as defined by claim 20, said atleast one other organic UV-screening agent being selected from the groupconsisting of: Ethylhexyl salicylate, Octocrylene, Phenylbenzimidazolesulfonic acid, Terephthalylidenedicamphorsulfonic acid, Benzophenone-3,Benzophenone-4, Benzophenone-5, 4-Methylbenzylidenecamphor, Disodiumphenyl dibenzimidazole tetrasulfonate, Anisotriazine, Ethylhexyltriazone, Diethylhexyl butamido triazone, 2,4,6-tris(Diisobutyl4′-aminobenzalmalonate)-s-triazine,Methylenebis(benzotriazolyl)tetramethylbutyl-phenol, Drometrizoletrisiloxane, and mixtures thereof.
 22. The photostablecosmetic/dermatological composition as defined by claim 1, furthercomprising at least one UV-screening coated or uncoated metal oxidepigment or nanopigment.
 23. The photostable cosmetic/dermatologicalcomposition as defined by claim 22, said at least one UV-screeningpigment or nanopigment comprising titanium oxide, zinc oxide, ironoxide, zirconium oxide, cerium oxide, and mixtures thereof.
 24. Thephotostable cosmetic/dermatological composition as defined by claim 1,further comprising at least one agent for artificially tanning and/orbrowning the skin.
 25. The photostable cosmetic/dermatologicalcomposition as defined by claim 1, further comprising at least oneadjuvant or additive selected from the group consisting of fattysubstances, organic solvents, ionic or nonionic thickeners, softeners,antioxidants, free-radical scavengers, opacifiers, stabilizers,emollients, silicones, α-hydroxy acids, antifoams, moisturizers,vitamins, insect repellants, fragrances, preservatives, surfactants,anti-inflammatories, substance P antagonists, fillers, polymers,propellants, acidifying or basifying agents, colorants, and mixturesthereof.
 26. The photostable cosmetic/dermatological composition asdefined by claim 1, formulated for photoprotecting the human epidermisand comprising a nonionic vesicular dispersion, an emulsion, a cream, amilk, a gel, a cream-gel, a suspension, a dispersion, a powder, a solid,a mousse or a spray.
 27. The photostable cosmetic/dermatologicalcomposition as defined by claim 1, formulated as a makeup for theeyelashes, the eyebrows or the skin and comprising a solid or pasty,anhydrous or aqueous formulation, or an emulsion, a suspension or adispersion.
 28. The photostable cosmetic/dermatological composition asdefined by claim 1, formulated for photoprotecting the hair againstultraviolet rays and comprising a shampoo, a lotion, a gel, an emulsionor a nonionic vesicular dispersion.
 29. A regime or regimen forphotoprotecting the skin and/or hair against the damaging effects of UVradiation, comprising topically applying thereon an effective amount ofthe photostable cosmetic/dermatological composition as defined byclaim
 1. 30. A method for enhancing the UV photostability of aphotolabile dibenzoylmethane sunscreen compound, comprising formulatingtherewith an effective amount of at least one 4,4-diarylbutadienecompound.